ECU wiring problems
Discussion
Hi
My Chimaera has been suffering from a rather odd problem that took many months to diagnose properly. It would occasionally cut out at random times, which was quite worrying when this happened on the motorway...
With the help of a TVR specialist, we found the problem to be that the ECU occasionally loses power, sometimes for a fraction of a second, sometimes longer, but doesn't always throw a fault code. The car does however almost always cut out and die.
Cleaning wiring and connections improved things for a bit but is expensive and difficult it seems, judging by the bill I got for that. I wondered whether you knowledgable folk know if there is a more permanent solution?
For example, if the ECU needs constant power connected to it, which I assume it does so it can remember long term lambda trim etc, then could I run a new power connection from the battery with an inline fuse and splice this into the power supply wire for the ECU? If so, does anyone know what size fuse I should be using, not wishing to damage the ECU to compund my problems?
Keen to see if you think this would work and anyone who might have experienced, seen or done something similar?
Many thanks
Pete
My Chimaera has been suffering from a rather odd problem that took many months to diagnose properly. It would occasionally cut out at random times, which was quite worrying when this happened on the motorway...
With the help of a TVR specialist, we found the problem to be that the ECU occasionally loses power, sometimes for a fraction of a second, sometimes longer, but doesn't always throw a fault code. The car does however almost always cut out and die.
Cleaning wiring and connections improved things for a bit but is expensive and difficult it seems, judging by the bill I got for that. I wondered whether you knowledgable folk know if there is a more permanent solution?
For example, if the ECU needs constant power connected to it, which I assume it does so it can remember long term lambda trim etc, then could I run a new power connection from the battery with an inline fuse and splice this into the power supply wire for the ECU? If so, does anyone know what size fuse I should be using, not wishing to damage the ECU to compund my problems?
Keen to see if you think this would work and anyone who might have experienced, seen or done something similar?
Many thanks
Pete
Hi Pete,
There are separate 12 Volt supply lines. The one that preserves long tern trim, etc. is not the problem, so I wouldn't bother making the mod you suggested. It seems that the main ignition-switched 12 Volts is probably cutting out. I would try replacing the relay since it's inexpensive and easy to do.
There are separate 12 Volt supply lines. The one that preserves long tern trim, etc. is not the problem, so I wouldn't bother making the mod you suggested. It seems that the main ignition-switched 12 Volts is probably cutting out. I would try replacing the relay since it's inexpensive and easy to do.
Thanks, already replaced the ECU relay (assuming that's the one you mean) a couple of times to no avail. It was the difficulty in finding any problem that meant I was looking into new wiring solutions!
I am a little confused though, as when the car cuts out, if this is caused by the 12v switched ignition side, I would expect it to still keep the lambda trim info, yet, when I plugged in Rover Gauge shortly after a recent failure, the trim values had all been reset, similar to unplugging the ECU?
Does anyone know if it is possible to run a parallel connection to the ECU spliced into existing wiring from the 12v ignition source, or am I about to find the immobiliser or something else in the way here?
Cheers
Pete
I am a little confused though, as when the car cuts out, if this is caused by the 12v switched ignition side, I would expect it to still keep the lambda trim info, yet, when I plugged in Rover Gauge shortly after a recent failure, the trim values had all been reset, similar to unplugging the ECU?
Does anyone know if it is possible to run a parallel connection to the ECU spliced into existing wiring from the 12v ignition source, or am I about to find the immobiliser or something else in the way here?
Cheers
Pete
Thanks Matt
Do you happen to know what was wrong with the ECU in detail for your friend's car? I have a 1993 4.0l car, so presume a 5.0l ECU would run it, although possibly not very well. I was thinking of just paying the circa £40 for the ECU to be tested, so as to try and eliminate that problem, so may explore this first, but thanks for the offer of an ECU loan, I may yet need to take that up!
It did seem a bit odd to me that the car lost its long term lambda history if the fault was on the switched ignition side. However, if it was on the permanent live feed, presumably the loss of this wouldn't cause the car to cut out?
Do you happen to know what was wrong with the ECU in detail for your friend's car? I have a 1993 4.0l car, so presume a 5.0l ECU would run it, although possibly not very well. I was thinking of just paying the circa £40 for the ECU to be tested, so as to try and eliminate that problem, so may explore this first, but thanks for the offer of an ECU loan, I may yet need to take that up!
It did seem a bit odd to me that the car lost its long term lambda history if the fault was on the switched ignition side. However, if it was on the permanent live feed, presumably the loss of this wouldn't cause the car to cut out?
Heres the manual for the 14CUX- you will see two feeds to the ECU, one switched ignition on the white / grey connection of the back of the main ECU plug, and one brown that is the 12 volt back up. Note this un switched supply appears to be the supply for the lambda heaters and fuel pump, so if you bypass it with another wire from the battery it will need quite a big fuse- at a guess 20 amp, as its not simply keeping power on the internal RAM.
http://www.g33.co.uk/images/PDFS/14cux_fuel_inject...
http://www.g33.co.uk/images/PDFS/14cux_fuel_inject...
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